Articles with one or more structured surfaces are useful in a variety of applications (e.g., abrasive discs, assembly of automobile parts, and disposable absorbent articles). The articles may be provided as films that exhibit, for example, increased surface area, mechanical fastening structures, or optical properties.
Mechanical fasteners, which are also called hook and loop fasteners, typically include a plurality of closely spaced upstanding projections with loop-engaging heads useful as hook members, and loop members typically include a plurality of woven, nonwoven, or knitted loops. Mechanical fasteners are useful for providing releasable attachment in numerous applications. For example, mechanical fasteners are widely used in wearable disposable absorbent articles to fasten such articles around the body of a person. In typical configurations, a hook strip or patch on a fastening tab attached to the rear waist portion of a diaper or incontinence garment, for example, can fasten to a landing zone of loop material on the front waist region, or the hook strip or patch can fasten to the backsheet (e.g., nonwoven backsheet) of the diaper or incontinence garment in the front waist region. Mechanical fasteners are also useful for disposable articles such as sanitary napkins. A sanitary napkin typically includes a back sheet that is intended to be placed adjacent to the wearer's undergarment. The back sheet may comprise hook fastener elements to securely attach the sanitary napkin to the undergarment, which mechanically engages with the hook fastener elements.
The hooks of mechanical fastening systems may be formed with a curved shape or they may be substantially upright stems that are deformed to include, for example, a head in the shape of mushroom. Some methods, which have varying degrees of versatility and complexity, are available to control the shape of loop-engaging heads. See, e.g., U.S. Pat. No. 3,192,589 (Pearson); U.S. Pat. No. 5,953,797 (Provost et al.); U.S. Pat. No. 6,132,660 (Kampfer); U.S. Pat. No. 6,558,602 (Melbye et al.) and U.S. Pat. No. 6,708,378 (Parellada et al.) and U.S. Pat. App. Pub. No. 2002/0124359 (Murasaki et al.).
Hook and loop fastening systems can include at least two engagement strength characteristics: peel strength and shear strength. Peel strength corresponds to the force required to disengage the fastening members from one another by peeling one fastening member upward and away from the other fastening member. Shear strength corresponds to the force required to disengage the fastening members from one another by pulling at least one of the fastening members away from the other in a plane that is parallel to the fastening members. Typically, the engagement strength of the fastening members is higher in shear than in peel.
When a user wishes to separate the hook and loop fastening members (e.g., on an absorbent article such as a diaper), typically the user peels the fastening members apart. The ease with which the fastening members can peel apart affects the user's perception of the reliability of the attachment between the fastening members. For example, when a caregiver removes a diaper from a baby, if the hook strip feels like it peels too easily from the loop landing zone or backsheet of the diaper, the caregiver may question how well the fastening members can keep the diaper closed when it is in use. And in some instances low peel strength can result in inadvertent separation of the fastening members while the diaper is being worn.
Despite the progress in hook and loop fastening technology, an enhancement in the reliability of the attachment between the fastening members, whether actual or perceived, would be desirable.